1. Field of the Invention
This invention relates to a method for operating a mass flowmeter that employs the Coriolis principle and encompasses a measuring tube through which flows a medium, wherein the measuring tube is stimulated into oscillating, and the resulting oscillatory response of the measuring tube is measured.
2. Description of Prior Art
A similar method has been described earlier for instance in DE 100 02 635 A1. According to that document, the measuring tube is stimulated in three mutually different oscillating modes, and by means of the recorded oscillatory response pattern of the measuring tube, the characteristic values of the mass flowmeter such as its zero point and its sensitivity are determined during the operation of the mass flowmeter with the aid of a mathematical-physical model.
Determining the zero point and sensitivity as the characteristic values during the operation of the mass flowmeter essentially serves the purpose of improving the accuracy of the mass flow measurements. But with a Coriolis-type mass flowmeter, it is additionally possible to measure the pressure of the medium flowing through the measuring tube. One approach frequently employed to that effect in conventional mass flowmeters has been to measure the expansion of the measuring tube, for instance with the aid of strain gauges. The pressure value thus obtained as an additional measured variable can be used, for instance, to correct for pressure-induced errors in other quantities to be measured. To be sure, this always requires additional pressure-measuring provisions such as the aforementioned strain gauges.